﻿#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <math.h>

typedef double Real;

typedef struct {
	int m;
	int n;
	int data[100000];
}Matrix;

typedef struct
{
	int n;
}Context;
Context context;
 

void read_data(Context* ctx)
{
	scanf("%d", &ctx->n);
}
 

void solve(Context* ctx)
{
	double s = 0;
	for (int i = 1; i <= ctx->n; ++i)
		s += sqrt(i);
	printf("sum = %.2f\n", s);
}

int main()
{
	freopen("D:/Develop/GitRepos/MOOC/浙江大学/数据结构/201906/DataStructure/M2019秋C入门和进阶练习集/7-170.txt", "r", stdin);
	read_data(&context);
	solve(&context);
	return 0;
}
